Apparatus and method for manufacturing reclosable bags utilizing zipper tape material

ABSTRACT

The present invention overcomes the shortcomings of the foregoing prior art devices and meets the foregoing needs by providing an apparatus and method for accurately sealing a multi-purpose reclosable zipper strip to a web of flexible film in an airtight manner. Moreover, the inventive apparatus and method is capable of repeatedly performing the steps necessary to seal tape to web with high throughout and with low cycle times. Generally, the apparatus and method utilizes a zipper tape having airtight splotch seals fused in series along desired lengths of the zipper tape. The zipper tape is dispensed through a feeding mechanism and, when an optical sensor detects one of the splotch seal portions of the zipper tape, a desired length of zipper tape is advanced over an elevator platform. A knife is then signaled to descend and sever the advanced portion of zipper tape, which is thus deposited onto the elevator platform. As the selected portion of the zipper tape is being positioned and deposited onto the elevator, the web is being positioned above the platform. A sealing head is then positioned over the web, while at the same time the elevator platform is driven upwardly so that the zipper tape portion positioned thereon comes into contact with the web. The heat passing through the web from the sealing head is sufficient to seal the peripheral portions of the zipper tape section to the web, thereby creating an airtight seal between the zipper tape portion and the web.

[0001] This application is based on and claims priority from U.S.Provisional Application Serial No. 60/250,885, filed Nov. 7, 2000.

FIELD OF INVENTION

[0002] The present invention relates to an apparatus and method forsealing zipper tape to a web of flexible film in an airtight manner.

BACKGROUND OF THE INVENTION

[0003] The popularity of reclosable zipper fasteners has created ademand for a large number and wide variety of reclosable bag sizes andtypes. It is commonly known in the art to form a reclosable bag throughthe addition of a zipper strip to a pair of bag walls in order to form abag with a reclosable, airtight seal. Transverse application of suchzipper strips to a web of flexible film (such as a web of plasticmaterial) is also known in the art.

[0004] In many reclosable bag applications, an airtight seal isnecessary in order to maintain the freshness and integrity of itemsstored within the bag. However, presently available reclosable bags donot provide or maintain an airtight seal as a result of leakage throughthe ends of the zipper strips, leakage through the seal between thestrip and the web, or leakage through the interlocked fastener profilesof the zipper strips themselves. There is thus a need for an apparatusand method for sealing a zipper strip to a web that reduces oreliminates the foregoing leaks. There is also a need for an apparatusand method for repeatedly and quickly sealing zipper tape to a web toallow for high-speed production of a web with pre-installed zipper-tapeto make the production of reclosable bags commercially viable.

[0005] Commonly known methods of construction and seal formation oftencause inaccurate, commercially unacceptable seals that cannot beproduced on an economically practical scale. Commonly known zipper stripformation methods require multiple sealing devices, precise machinery orextensive retooling to alter the size and type of reclosable fastener.Examples of such devices and methods are described in U.S. Pat. Nos.5,601,368 (Bodolay), 3,847,711 (Howard), 5,461,845 (Yeager), 4,241,865(Ferrell), 4,335,817 (Bahr), 4,909,017 (McMahon) and 5,024,537 (Tilman).None of the foregoing devices and methods satisfy the need for amulti-purpose reclosable zipper strip that can be accurately andeconomically sealed in an airtight manner to a web of flexible film.

BRIEF SUMMARY OF THE INVENTION

[0006] The present invention overcomes the shortcomings of the foregoingprior art devices and meets the foregoing needs by providing anapparatus and method for accurately sealing a multi-purpose reclosablezipper strip to a web of flexible film in an airtight manner. Moreover,the inventive apparatus and method is capable of repeatedly performingthe steps necessary to seal tape to web with high throughout and withlow cycle times.

[0007] Generally, the apparatus and method utilizes a zipper tape havingairtight splotch seals fused in series along desired lengths of thezipper tape. The zipper tape is dispensed through a feeding mechanismand, when an optical sensor detects one of the splotch seal portions ofthe zipper tape, a desired length of zipper tape is advanced over anelevator platform. A knife is then signaled to descend and sever theadvanced portion of zipper tape, which is thus deposited onto theelevator platform.

[0008] As the selected portion of the zipper tape is being positionedand deposited onto the elevator, the web is being positioned above theplatform. A sealing head is then positioned over the web, while at thesame time the elevator platform is driven upwardly so that the zippertape portion positioned thereon comes into contact with the web. Theheat passing through the web from the sealing head is sufficient to sealthe peripheral portions of the zipper tape section to the web, therebycreating an airtight seal between the zipper tape portion and the web.

DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a front perspective view of a preferred embodiment ofthe apparatus of invention for sealing zipper tape to a web of flexiblefilm;

[0010]FIG. 2 is a partial front perspective view of the apparatus ofFIG. 1 showing a pneumatically-actuated elevator for placing the zippertape of the present invention against the web;

[0011]FIG. 3 is a partial front perspective view of the apparatus ofFIG. 1 showing the pneumatically-activated elevator of FIG. 2 having anopening in the center thereof for reception of a sealing head from abovethe web;

[0012]FIG. 4 is a top perspective view of a sealing head and perforationdie positioned above the web, with the sealing head positioned to theside of the elevator and the perforation die positioned over theelevator;

[0013]FIG. 5 is a top perspective view of a sealing head and perforationdie positioned above the web, with the sealing head positioned over theelevator and the perforation die positioned to the side of the elevator;

[0014]FIG. 6 is a side perspective view of the apparatus of FIG. 1;

[0015]FIG. 6A is a front plan view of the apparatus of FIG. 1;

[0016]FIG. 6B is a front perspective view of a computer used to controlthe apparatus of FIG. 1;

[0017]FIG. 7 is a front plan view of a bag manufactured using thepresent invention;

[0018]FIG. 8 is a side cutaway view of the bag of FIG. 7;

[0019]FIG. 9 is a front perspective view of the preferred embodiment ofthe zipper tape of the present invention showing the fastener profilesof the first and second fastener strips;

[0020]FIG. 10 is a front perspective view of the zipper tape of FIG. 9showing a series of interconnected zipper tape sections having splotchsections between each section; and

[0021]FIG. 11 is a front perspective view of a zipper tape applicationdevice applying tape to a web of film that is subsequently wound on awinder for later use in a bagging machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0022] The preferred embodiment of inventive apparatus 120 (best shownin FIGS. 1 and 6) is capable of accurately sealing a multi-purposereclosable zipper strip 100 to a web 110 of flexible film in an airtightmanner. Moreover, apparatus 120 is capable of repeatedly performing thesteps necessary to seal tape 100 to web 110 with high throughout andwith low cycle times.

[0023] Zipper tape 100 is preferably constructed of polyethylene and mayalso include additives such as ethylene acetate to facilitate easysealing. Web 110 is also preferably constructed of polyethylene, but maybe constructed of other commonly known films, such as polyproplene orpolyethylene terepthalate (Saran®), or any other material providing asealing layer that is compatible with the zipper tape 100.

[0024] As shown in FIG. 9, zipper tape 100 comprises (1) a continuoussupply of first profile strip 100A; and (2) a continuous supply ofsecond profile strip 100C opposite the first profile strip 100A. Thefirst profile strip 100A includes at least one rib 100B protruding fromand along the length of the inner surface of first profile strip 100A.The second profile strip 100C includes at least two ribs 100D and 100Efor sealably receiving rib 100B. Ribs 100D and 100E protrude from andalong the length of the inner surface of second profile strip 100C. Asshown in FIG. 10, a series of splotch seal portions 100F are fused alongdesired lengths of the first profile strip 10A, the second profile strip100C, and ribs 100B, 100D, and 100E.

[0025] As seen in FIG. 6, zipper tape 100 is stored on roll 130, fromwhich it is fed through apparatus 120 by a servometer 140, whichcontrols the acceleration, speed and deceleration of zipper tape 100'smovement through apparatus 120. Zipper tape 100 is wound through aseries of dancer rollers 150 on arm 160, which allow zipper tape to befed into feeding mechanism 170 at the desired tension. In a preferredembodiment, a photosensor 162 reads the position of the dancer arm 160and, when the arm is descended to a desired position, advances zippertape 100 using nip drive 166.

[0026] Feeding mechanism 170 utilizes an optical sensor 180 to detectthe presence of the splotch seal portions 100F. Optical sensor 180detects the thickness of the zipper tape 100 and is thus able to detectand distinguish each splotch seal portions 100 because such portions arethinner than the remainder of zipper tape 100. The splotch seal portions100 thus act as eye marks to indicate the position of zipper tape 100.

[0027] When optical sensor 180 detects one of the splotch seal portions100F of zipper tape 100, it signals belt tracks 340 and 350 (see FIG.3), which utilize belt drive 360 to advance a desired length of zippertape 100 over elevator 230. In the preferred embodiment, optical sensor180 utilizes a piezo-electric bridge 390 (FIG. 6) to convert changes inopacity of the zipper tape 100 at the thinned portions (splotch sealsections 100F) to an electrical signal to advance zipper tape a desiredlength. Guillotine knife 370, driven by another servomotor 410, is thensignaled to descend and cut portion 390 of zipper tape 100. Section 390of zipper tape 100 thus positioned over and deposited onto elevator 230.Both the operation of belt drive 360 and guillotine knife can besequenced using pneumatic control devices such as those MatrixTechnologies or by utilizing a computer control system such as thosemanufactured by Allen Bradley.

[0028] As shown in FIG. 3, in a preferred embodiment, the top surface ofelevator 230 comprises a rectangular platform 240 for receiving section390 of zipper tape 100. As the selected portion 290 of zipper tape 100is being positioned and deposited onto platform 240 in the foregoingmanner, web 100 is being positioned above platform 240 as shown in FIG.4. A series of eye marks is printed along one edge of web 100 and aredetected by a second optical sensor 190. A roll of web 100 is advancedthrough apparatus 120 by a series of roll drivers 200, which are drivenby a second servomotor 210. The speed of drive rollers 200 iscoordinated by the sensor 190 and a computer 220 (shown in FIG. 6B), sothat a desired portion of web 110 is positioned over elevator 230 toreceive the selected portion 390 of zipper tape 100.

[0029] In one embodiment, web 110 is mounted on a roller 530 (see FIG.6). As web 110 is pulled through a series of dancer rolls 540 (FIG. 3)mounted on arm 560, drive rollers 570 (FIG. 6A) pull web 100therethrough. When additional web material is pulled through rollers570, the upstream dancer arm 520 rises, causing coils 522 in springs 524to stretch under tension. When the arm 520 reaches a preset position,drive rollers 520 are deactiviated. The coils under tension pull the arm520 down to receive the material being advanced through the three-loopdancer roll assembly 540 and the process is then repeated.

[0030] In the preferred embodiment, elevator 240 is contained within ahollow Lexan® pedestal 242 defining a central opening 244 in which theelevator is 240 is positioned. A pair of rectangular ledges 248 and 249are located at the top of pedestal 242. When the selected portion of web110 is fed into position over elevator 240, the selected portion of web110 extends over and between ledges 248 and 249.

[0031] As shown in FIG. 4, a pneumatically-controlled sealing head 270is mounted on block 280, which in turn is slidably mounted on shaft 291.As shown in FIG. 4, sealing head 270 and block 280 are positioned aboveledges 248 and 249 and to the side of platform 240. Following thedeposit of section 290 of zipper tape onto platform 240 and thepositioning of web 110 above platform 240, block 280 is drivenhorizontally by air cylinder 320 until sealing head 270 is positionedabove platform 240 and, preferably, in contact with web 110. Sealinghead 270, which is preferably Teflon® coated, is then either heated tothe desired sealing temperature or is maintained at the desired sealingtemperature.

[0032] At the same time, elevator 230 is driven upwardly by shaft 400until platform 240 (and the zipper tape portion 390 thereon) is incontact with web 110. The heat passing through the web 110 from thesealing head 270 is sufficient to seal the peripheral portions ofportion 290 of zipper tape 100 (as seen in FIG 10) to web 110, therebysealing the zipper tape portion 290 positioned on the platform to web110. Sealing head 270 further aids in creating the seal by providing astable surface against which the elevator 230 can compress the web 110and zipper tape portion 290.

[0033] The resulting seal is airtight due to the construction of zippertape 100, which has thickened flanges 100G that melt and fill any gapsduring sealing. Section 290 of zipper tape 100 is also airtightthroughout the zipper portions because of the unique construction of thezippers themselves, as disclosed in parent U.S. patent application Ser.No. 09/415,696, incorporated herein by reference.

[0034] In one embodiment, a pneumatically controlled perforation knifeis mounted to block 270. When air cylinder 300 is actuated, perforationknife 260 descends downwardly so that knife 260 perforates web 110between ledges 248 and 249, which serve as an, anvil against which web110 is severed by knife 260. The air cylinder 300 then retractsperforation knife. In a preferred embodiment, sealing head 270 andperforation knife 260 may be combined so that the perforation of web 110and the sealing of zipper tape portion 290 may be accomplishedsimultaneously. Alternatively, the sealing head 270 can be moved intoplace over platform 240 after the web has been severed by knife 260. Inanother embodiment, web 110 is not perforated, but is fed and wound ontoa winder 80 to create a zippered roll stock 590 with zipper tape alreadysealed on base web for later use in a bagging machine 510 (see FIG. 11).

[0035] While the present invention has been disclosed in terms of thepreferred embodiments in order to facilitate better understanding of theinvention, it should be appreciated that the invention can be embodiedin various ways without departing from its basic principles. Therefore,the invention should be understood to include all possible embodimentsand modifications to which do not depart from the invention as set outin the appended claims.

We claim:
 1. A method of making a reclosable plastic bag comprising:feeding a zipper tape having at least one splotched portion thereofacross a sensor; detecting said splotched portion to obtain a signal;and actuating a cutter for cutting said zipper tape in response to saidsignal to create a selected portion of the zipper tape.
 2. The method ofclaim 1 wherein said step of detecting comprises determining a thicknessof said splotched portion.
 3. The method of claim 2 in which said stepof determining comprises comparing said thickness to a referencepredetermined thickness.
 4. The method of claim 1 further comprisingsplotching said zipper tape multiple times to create a series ofsplotches along the length of the zipper tape.
 5. The method of claims1, 2 or 4 further comprising sealing said selected portion of the zippertape to a web.
 6. An method for sealing a portion of a zipper tape to aweb, the method comprising: providing an elevator having a platform forreceiving the portion of zipper tape; depositing the portion of zippertape onto the platform; positioning a section of the web above theplatform; positioning a sealing head over the web section for heatingthe web section; and elevating the platform towards the web sectionuntil the portion of zipper tape comes into contact with the websection, thereby forming a seal between at least a portion of theportion of the zipper tape and the web section.
 7. The method of claim 6wherein said sealing head is in contact with the web section when theportion of zipper tape comes into contact with the web section.
 8. Themethod of claim 6 further comprising the step of perforating the websection.
 9. The method of claim 8 wherein the web section is perforatedby a knife positioned above the web section.
 10. The method of claim 8wherein the web section is perforated prior to the portion of zippertape being sealed to the web section.
 11. The method of claim 6 whereinthe seal is substantially airtight.
 12. The method of claim 6 whereinthe seal is substantially watertight.
 13. The method of claim 6 whereinthe portion of zipper tape is created by feeding a zipper tape having atleast one splotched portion thereof across a sensor, detecting saidsplotched portion to obtain a signal, and cutting said zipper tape inresponse to said signal to create the portion of zipper tape.
 14. Themethod of claim 6 wherein the method is repeated to seal a plurality ofzipper tapes to the web and further comprising the step of winding theresulting web onto a winder.
 15. An apparatus for sealing a portion of azipper tape to a web section, the apparatus comprising: an elevatorhaving a platform for receiving the portion of zipper tape; means fordepositing the portion of zipper tape onto the platform; means forpositioning the web section above the platform; and a sealing headpositioned over the web section for heating the web section, wherein theplatform can be elevated towards the web section until the portion ofzipper tape comes into contact with the web section to form a sealbetween at least a portion of the portion of the zipper tape and the websection.
 16. The apparatus of claim 15 wherein the sealing head is incontact with the web section when the portion of zipper tape comes intocontact with the web section.
 17. The apparatus of claim 15 furthercomprising a cutter for perforating the web section.
 18. The apparatusof claim 17 wherein the cutter comprises a knife positioned above theweb section.
 19. The apparatus of claim 15 wherein the seal issubstantially airtight.
 20. The apparatus of claim 15 wherein the sealis substantially watertight.
 21. The apparatus of claim 15 wherein thezipper tape has at least one splotched portion and further comprising asensor for detecting the splotched portion to obtain a signal, and acutter for cutting said zipper tape in response to said signal to createthe portion of zipper tape.